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Copper(I) halides are often added to olefin metathesis reactions to inhibit catalyst degradation, control product isomerization, enhance catalyst activation, or facilitate catalyst dimerization. In each of these examples, the copper salt is presumed to operate as an independent species, separate from the ruthenium center. We have discovered, however, that certain copper salts can form complexes with the ruthenium catalyst itself, forming hetero-bimetallic copper-ruthenium olefin metathesis catalysts. We confirmed the formation of two complexes through single-crystal X-ray crystallography and NMR spectroscopy. The crystal structure revealed the presence of a four-member ring containing ruthenium, carbon, copper, and chlorine or bromine. The hetero-bimetallic catalyst displayed higher latency and lower activity in the ring-opening metathesis polymerization (ROMP) of norbornene compared to analogous monometallic catalysts. For example, norbornene polymerization catalyzed by the monometallic complex reached 80 % conversion after 4 h, but only 12% conversion when catalyzed by the hetero-bimetallic copper-ruthenium complex under the same conditions. Conversion increased to 63 % when the temperature increased to 50 °C for 1 h, indicating that the bimetallic complex retains activity but requires a higher temperature to activate. The formation of these copper-ruthenium bimetallic complexes suggests the possibility of multi-metallic olefin metathesis catalysts, potentially with different activity and properties than their traditional monometallic counterparts.
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Electrochemically Controlled Ruthenium-Catalyzed Olefin Metathesis
Abstract The development of a system to electrochemically control ruthenium-catalyzed olefin metathesis is reported. Catalyzed by a commercially-available bis-NHC Ru complex, this system displays a broad substrate scope with very short reaction times, as well as excellent levels of temporal control over metathesis with only electricity as a stimulus.
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- Award ID(s):
- 2102672
- PAR ID:
- 10525815
- Publisher / Repository:
- Thieme
- Date Published:
- Journal Name:
- Synlett
- Volume:
- 34
- Issue:
- 12
- ISSN:
- 0936-5214
- Page Range / eLocation ID:
- 1477 to 1481
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1055/s-0042-1751469
